Intra-pertitoneal injections of ethanol (50 umoles/ml body water) Sodium D(-) lactate (25 umoles/ml body water), amd pentobarbital (15mg/kg rat) into 48 hours fasted male wistar rats produced anesthesia in about 15 minutes. Compared to controls, rats under ethanol and sodium D(-)lactate and sodium pentobarbital anesthesia showed a significant 40 to 50 percent decrease in theri brain mitochondrial redox potential as assessed from a change in the NAD+/NAHD ratio. The cytosolic redox potential remained unchanged with a lactate/pyruvate ratio ranging from 15 to 23. The cytosolic phosphorylation potential was not significantly different between the ethanol group, the D(-) and L(+) lactate groups, pentobarbital group and the controls. On the basis of a decreased mitochondrial NAD/NADH ratio, the current working hypothesis is that ethanol, D-lactate and Na-pentobarbital all exert a common effect to induce anesthesia by causing a partial inhibition of electron transport. This suggestion would help explain why tissues like the brain and heart accumulate NADH, even though in contrast to the liver, they lack alcohol dehydrogenase.